Host life history traits as drivers of viral infection in European bats.

Bats are recognized as natural reservoirs of a wide range of viruses. Understanding the factors that determine patterns of viral occurrence in reservoir species, particularly viral richness and viral detection frequency, is essential for explaining host-pathogen dynamics and anticipating public health risks. In this study, we evaluated the influence of life-history traits on viral frequency (defined as the proportion of positive detections across studies) in European bats for six important viral groups (Adenoviridae, Herpesviridae, Papillomaviridae, Filoviridae, Coronaviridae, and the genus Lyssavirus within Rhabdoviridae) through a systematic review, identifying 7,037 publications, of which 155 met the inclusion criteria. These studies focused primarily on three species: Cnephaeus serotinus, Myotis daubentonii, and Pipistrellus pipistrellus. We detected a phylogenetic signal in viral frequency only for the family Adenoviridae and genus Betacoronavirus, suggesting that these viral groups have a particular evolutionary affinity with their hosts. Viral frequency was associated with bats' environmental breadth and body size, although these relationships were not consistent across all viral groups. Instead, each viral group was associated with a distinct set of host life-history traits, reflecting -most probably- differences in their ecology and evolutionary history. Overall, our findings demonstrate that the ecological drivers of viral frequency are virus-specific rather than universal.